What it measures
HbA1c measures how much of the haemoglobin in red blood cells has glucose attached. Because red cells last about three months, it reflects average blood sugar over the past two to three months rather than at the moment of the test.
Why people test it
- Used to diagnose type 2 diabetes and to spot raised blood sugar before diabetes develops.
- Monitored regularly in people with diabetes to follow blood sugar over time.
- Checked when there are risk factors, such as a family history of diabetes.
- Checked in people taking medicines that can raise blood sugar, such as steroid tablets.
Typical range
Ranges and cut-offs can vary between labs, and your report shows the lab's own range. One NHS trust's lab reads below 42 mmol/mol as non-diabetic, 42 to 47 as an increased risk of diabetes, and 48 or above as consistent with diabetes. Source: Royal Liverpool University Hospital pathology: Glycated haemoglobin.
Finger-prick or vein?
A finger-prick sample is usually fine for HbA1c, and no fasting is needed because it reflects the past few months.